1. Field of the Invention
This invention relates to apparatus used in the mooring of structures to the soils underlying bodies of water, referred to as waterbottoms. More specifically, this invention relates to a type of anchor particularly, although not exclusively, suitable for so-called “gravity installation,” where the anchor is released at a desired height above a water bottom and allowed to fall to and penetrate into the waterbottom.
2. Description of Related Art
Different types of anchors, especially suited for the mooring of floating structures, have long been in use. Some anchors rely on their weight for holding capacity. Others have flukes which tend to drive the anchor into the waterbottom when a tension is applied to a mooring line. Still others embed into the waterbottom by a suction process.
Another type of anchor which is employed for mooring purposes is the so-called gravity installed anchor, which is lowered from the surface of a body of water to a desired height above a waterbottom, and then released to fall to and penetrate into the waterbottom. The inertia of the anchor carries it into the soils comprising the waterbottom. Thereafter, a tension can be applied to a mooring line connected to the anchor. Examples of such anchors known in the art include U.S. Pat. No. 6,106,199 to Medeiro, Jr. et al (Aug. 22, 2000) and U.S. Pat. No. 6,257,166 to Lieng (Jul. 10, 2001). The anchors disclosed therein comprise a generally circular in cross section central body, with a plurality of fins or blades connected to the central body. Such anchors lack the advantages presented by the present invention. One disadvantage of the prior art gravity-installed anchor designs is that a significant amount of penetration into the soil is required for adequate holding capacity. Typically, prior art designs require penetration depths (into the soils) well in excess of the longitudinal length of the anchor. The anchor of the present invention generally only requires penetration just beyond its full length, typically half that required by other gravity installed anchors.
In addition, mooring line attachment points to such anchor designs are limited to top (that is, the uppermost end) or fixed side attachments. Top attachments do not require any particular alignment with the mooring line direction since the pull can be from any direction; however, the top attachment greatly reduces holding capacity. Side attachments yield greater holding capacity, however current designs require accurate attachment point orientation (that is, the attachment point must be aligned with the direction of mooring line pull). Angular alignment of the side attachment point with the mooring line pull can be difficult to achieve in field applications. The present invention preferably comprises a mooring line attachment which can rotate completely around the body of the anchor, and further comprises a hinged arm, eliminating problems related to installation orientation. Further, the arm reduces the likelihood of the mooring line being caught on the anchor plates. Yet another advantage of the present invention is that a single anchor can be adjusted to vary the exposed nose and tail plate areas, thereby rendering the anchor suitable for various applications, soil types, or soil strength gradients.